Heavy duty swivel platform conveyor

ABSTRACT

A heavy-duty swivel platform conveyor such as may serve as a helicopter landing pad on a ship deck includes a platform structure, transporting longspan screw device under the platform fixed to the deck or other base and with driving couplings with the platform enabling swiveling of the platform relative to the path along which the platform is adapted to be transported by operation of the longspan screw.

United States Patent [1 1 Leming et a1.

[ HEAVY DUTY SWIVEL PLATFORM CONVEYOR [76] Inventors: John C. Leming,25180 Stratford Rd., Glen Ellyn, 111. 60137; Donelson C. Glassie, 3810Bradley Ln., Chevy Chase, Md. 20015; Roy M. Jahnel, 2016 Jameson St.,Washington, DC. 20031 [22] Filed: Apr. 21, 1972 [21] Appl. No.: 246,460

[52] US. Cl 114/43.5, 74/58, 74/89.15,

74/479, 244/116 [51] Int. Cl 1363b 35/50 [58] Field of Search 114/435;244/114,

244/115, 116; 214/8324; 74/89.l5, 58, 479; 115/1 R; 105/367, 368 R, 455

[56] References Cited UNITED STATES PATENTS 1,812,237 6/1931 Garcia244/116 2,573,496 10/1951 Runkle 214/8324 Jan. 15, 1974 2,483,121 9/1949Bourassa 74/58 3,382,836 5/1968 Hume 115/1 3,568,957 3/1971 Wood74/89.15

FOREIGN PATENTS OR APPLICATIONS 928,409 6/1963 England 244/1 14 PrimaryExaminer-Duane A. Reger Assistant ExaminerGalen L. BarefootAttorney-Benjamin H. Sherman et al.

[57] ABSTRACT A heavy-duty swivel platform conveyor such as may serve asa helicopter landing pad on a ship deck includes a platform structure,transporting longspan screw device under the platform fixed to the deckor other base and with driving couplings with the platform enablingswiveling of the platform relative to the path along which the platformis adapted to be transported by operation of the longspan screw.

18 Claims, 7 Drawing Figures 1 HEAVY DUTY SWIVEL PLATFORM CONVEYOR Thisinvention relates to heavy-duty conveyors, and is more, particularlyconcerned with swivel platform conveyors adapted to be efficientlyoriented with the direction of approach thereto of a mobile object to bereceived on the platform for transportation along a fixed path to adifferent position than that at which the object is received on theplatform.

Although it will be apparent as the description proceeds that thepresent invention may have numerous and varied uses, an especiallyadvantageous use, selected by way of example, involves the provision ofa heavy-duty swivel platform conveyor especially adapted to serve as alanding pad for aircraft of the vertical take-off and landing type, suchas helicopters, enabling transporting of the aircraft to and from atakeoff and landing position and a storage position.

A special problem exists in respect to landing pads on shipboard whereit is necessary to operate on limited deck space and often under adverseweather conditions. Due to wind and course conditions it is oftennecessary to take off and land the aircraft at angles that may varywithin 30 from the ship axis. Take-off and landing operations areespecially difficult in rough weather, high seas and strong windsituations. Handling of the aircraft on deck under adverse conditionscan be quite hazardous due to tendency of the aircraft to slide or tipas caused by ship roll, heaving, pitching, wind effects, waves washingover the deck, and the like. Most of these hazards are experienced notonly on the open dock, but also in the parking area or hangar.

An important object of the present invention is to overcome theforegoing and other disadvantages, deficiencies, inefficiencies,shortcomings and problems in prior methods and structures and to attainimportant advantages and improvements as will hereinafter becomeapparent.

Another object of the invention is to provide a new and improvedapparatus and method especially suited to handling heavy mobile objects,and more particularly aircraft of the generally vertical take-off andlanding type, such as helicopters.

A further object of the invention is to provide a new and improvedheavy-duty swivel platform conveyor construction.

Still another object of the invention is to provide a new and improvedconveyor construction utilizing long span screw assemblies.

Yet another object of the invention is to provide a new and improvedheavy-duty swivel platform conveyor embodying a novel swiveling controlmechanism.

A still further object of the invention is to provide a new method ofhandling aircraft between a landing and take-off position and a storageor parking position.

Other objects, features and advantages of the invention will be readilyapparent from the following description of certain preferred embodimentsthereof, taken in conjunction with the accompanying drawings, althoughvariations and modifications may be effected without departing from thespirit and scope of the novel concepts embodied in the disclosure, andin which:

FIG. 1 is an illustrative view showing a heavy-duty swivel platformconveyor embodying features of the invention utilized as a shipboardlanding and take-off pad for aircraft such as helicopters;

FIG. 2 is a top plan view of the platform;

FIG. 3 is a schematic view of one form of long-span screw drive that maybe employed in operating the platform;

FIG. 4 is a schematic illustration of another form of screw driveadapted for the present purpose;

FIG. 5 is an enlarged fragmentary sectional detail view takensubstantially along the line VV of FIG. 2;

FIG. 6 is a fragmentary sectional detail view taken substantially alongthe line VI-VI of FIG. 5; and

FIG. 7 is a representative schematic illustration of electrical controlcircuitry for operating the conveyor system.

On reference to FIGS. 1 and 2, an illustrative heavy duty swivelplatform conveyor system 10 is depicted as especially adapted for use ona landing deck area 11 of a sea-going vessel 12 such as an aircraftmother ship,

. patrol ship, rescue ship, cruiser, destroyer, and the like.

At one end of the area 11 may be provided an aircraft hanger 13 forservicing or storage parking of an aircraft such as a helicopter 14.

Construction of the platform 10 is suitable to meet the service andoperating conditons for which intended. For example, as an aircrafthandling device, and more particularly as a snare pad for helicopters,it must be capable of withstanding aircraft loads of on the order of sixtons with surface dimensions of about 24 feet width and 35 feet length.It must also in a shipboard system be capable of withstanding wind, waveand water loads should ship roll and sea state combine to put greenwater over the deck. Ship roll and pitch will also impose forces andstrains which must be successfully met. To this end, the platform 10comprises a sturdy steel beam or bar frame 15 carrying fixedly thereon asuitable supporting surface 17 which may comprise steel plate but forshipboard use is desirably a heavy metal grid or grating structure.Where the space, such as the hanger 13 will not accommodate the totallanding pad width of the platform 10, one or both opposite longitudinalsides thereof may be provided with respective extensions 18 therealongconnected to the main body of the platform by means of hinge joints 19so that they can be swung up from a flat planar relationship as depictedin full line in FIG. I to a generally upright relationship as shown indash outline whereby to clear the inner sides of the hangar 13.

Means are provided for enabling traverse of the platform along the deck11 between parking position within the hangar l3 and take-off andlanding position out on the deck clear of the hangar, as well as toenable swiveling of the platform in a desirable range from itslongitudinal traverse path axis. For this purpose, transporting screwmeans 20 are provided adapted to be mounted in a fixed path below theplatform 10. In a preferred form, the screw means 20 are of the longspan type disclosed in John C. Lemings US. Pat. No. 3,670,583 issuedJune 20, 1972. In this instance a pair of the screw assemblies 20 isprovided in spaced parallel relation extending from as far within thehangar l3 as necessary to as far out on the deck 11 as necessary. Eachof the screw assemblies 20 includes a series of corotatively connectedscrew sections 21 (FIGS. 2 and 5) rotatably supported by hangers orbrackets 22. To maintain the deck 11 clear of obstruction, the screws 20are mounted below the surface of the deck, desirably in channels 20a.

Means for operatively coupling the platform 10 with the screw means fordriving the platform along the path by operation of the screw meanscomprise respective nuts 23 (FIGS. 2,5 and 6) which are non-rotatablycoactive with and adapted to travel freely linearly along the respectivescrews. Each of the nuts 23 comprises a body 24 provided with alongitudinal clearance bore of a diameter to receive the transportingscrew therethrough in free spaced relation, with contact between the nutand the screw limited to useful work engagement between followers 27carried by the body 24 and projecting operatively into the threads ofthe screw. For clearing the stationary supporting brackets 22, a narrowbracket-clearance slot 28 is provided radially in and throughout thelength of the body 24 extending from the screw clearance bore to theouter perimeter of the nut. Through this arrangement, rotation of thescrew 20 in either rotary direction effects corresponding longitudinaltravel of the nut 23 therealong. In such travel of the nut along thescrew a stabilized substantially concentric spaced friction freerelation therebetween is maintained by nut supporting and guiding meanscomprising a roller and track arrangement wherein the body 24 isprovided with rollers 29 running along tracks provided by rail bars 30rigid with the sides of the channels 23. For maximum stability and loadsupporting value, the nut bodies 24 are elongated with a plurality ofrollers along each side, desirably comprising two pairs of rollers alongeach side with one pair adjacent one end and the second pair adjacentthe opposite end and with each pair of rollers having its axis divergentto its companion so as to run along correspondingly divergently relatedlongitudinal, oblique respective track surfaces 31 on the rails 30.

Both of the nuts 23 are connected to the platform 10 in a manner toenable driving of the platform longitudinally along the screws 20, andalso to enable pivoting of the platform relative to the path of movementas desired. To this end, each of the nuts 23 carries an upstandingcoupling and swivel stud 32 (FIG. 5). One of the nuts 23 has aconnection 33 (FIG. 2) at a suitable fixed location along a transverseplatfrom frame bar 34, while the other of the nuts 23 is pivotallyconnected by its swivel stud 32 with a runner carriage block 35constructed on the order ofthe nut bodies 24, of generally elongatedform and having a similar arrangement of pairs of anti-friction wheels37 arranged to run along respective transversely oblique track surfaces38 on rail bars 39 carried by the bar 34 which is in the form of aninverted channel for this purpose. By having the body of the platformframe 15 wider than the spacing between the screws 20, and the channelframe bar 34 even a slight bit longer than the width of the frame body,as by having the bar 34 disposed at an oblique angle relative to theaxis of the frame, as shown in FIG. 2, with swiveling of the frame aboutthe fixably located pivot 33, and movement of the runner 35 along therails 39 as required, a full range of pivoting within the desiredparameters, to the left or right of the screworiented traverse path isenabled. For example, the pivotal range may be on the order of 30 ineither direction from the longitudinal centerline or axis of thetraverse path provided by the screws 20.

Direct support of load from the platform 10 to the deck 11 is primarilythrough anti-friction means in the form of casters 40 (FIGS. 2 and 5)properly placed to afford stable loading without strain upon thecouplings with the screws 20. Placement of the casters 40 is such thatin every pivotal position and in the straight inline position of theplatform 10 relative to the screws 20, the casters make contact with thedeck, or at least a sufficient number of the casters will always be incontact with the deck to sustain the load. Inasmuch as the screwaccommodating channels 23 are of relatively narrow width, there islittle likelihood of the platform being swivelled to a position whereinmore than one of the casters may be suspended in the space over one ofthe channels. At least at the rear end portion of the platform 10 thecasters are disposed with full assurance of at least two of them, spacedtraversely across the platform, being in full load sustaining engagementwith the deck 11 in any swivelled position of the platform. Additionalmeans are provided .to provide at least some load sustaining capability,and in any event stabilization of the platform 10 in any positionthereof relative to the path of the longitudinal movement, as well asthorough anchorage to the deck resistive of any forces that might tendto lift the platform. Accordingly, at each side of the transversechannel member 34, a generally V-shaped inverted channel-shaped runnerbar assembly 41 is provided having configuration the same as the bar 34.The bar assemblies 41 are in allochiral relative relattionship with eachleg of the assembly accommodating a wheeled runner block 42 thereinpivotally connected to an associated wheeled traveling block 43 to runalong the underlying rails 30. Each of the stabilizing runner assemblies42,43 may be of the same construction as the swivel and coupling nut 23and the associated runner block 35, and the description for thatassembly may be considered the same as the details for the stabilizers42,43 with the exception that the traveling blocks 43 will not serve asnuts and thus be free from any followers coacting with the screws.Thereby, the traveling blocks 43 can move longitudinally relative to thescrews 20 freely, without regard to the direction of rotation of thescrews. Further, thereby the traveling block and runner assemblies canshift freely relative to one another, and to the screws 20 and to theframe of the platform, along the track provided by the stabilizer railchannel bar assemblies 41.

Traverse and pivotal movements of the platform 10 are effected byrotation of the screws 20, unison rotation of the screws in eitherdirection causing corresponding traverse movement of the platform, androtation of one of the screws while the other remains stationary orrelative opposite hand rotation of the screws causing swiveling movementof the platform. For example, considered from the viewpoint of facingtoward the hangar l3, movement of the platform 10 from the straight inline traverse position to the angular position shown in FIG. 2 can beeffected by holding the right hand screw 20 stationary while the lefthand screw is rotated to advance the left hand coupling nut 23rearwardly, or for very rapid swiveling, the left hand screw can beoperated to move the left hand coupling nut rearwardly while the righthand screw is operated simultaneously to advance the right hand couplingnut 23 forwardly. To effect swiveling in the opposite direction, justthe reverse action of the screws is affected.

Driving of the screws 20 may be effected at their forward end, which, inthis instance, will be inside the hangar l3. Desirable means for thispurpose comprise, as shown in FIG. 3, for each screw, a variable speedmotor 44 having a brake 45 adapted to be remotely controlled andpositively locked by the brake 45 when not called upon to drive theassociated screw. Driving power from the motor is transmitted through ashaft 47 and a gear box 48 having therein a reduction and reversing geartrain and including a clutch arrangement including neutral position 49,a forward clutch element 50 and a reversing clutch element 51 andconnected by a transmission shaft 52 and a coupling 53 with theassociated screw 20. Normally on screw brake 54 and a control clutch 55are provided on and in association with the transmission shaft 52 formanual override when necessary. A manually operated clutch 57 isprovided in the shaft 47, and a manually operable gear train 58 in theportion of the shaft 47 which is disengageable through the clutch 57from the motor attached portion of the shaft.

In a relatively more simple arrangement shown in FIG. 4, the motor 44may be of the reversable type driving the screw 20 without a gear traintransmission so that the shaft 47 is directly coupled by the coupling 53to the screw and with the normally on brake 54, the control clutch 55,the manual clutch 57 and the manual drive 58 provided on and along theshaft.

Electrical control circuitry for the swivel platform conveyor operatingsystem may be generally in accordance with that shown in FIG. 7. Amaster control switch 60 which may be in the form ofa circuit breakercontrols power to a full wave bridge silicon rectifier 61 which may be240 volt single phase connected with the motors 44 adapted to power therespective long span drive screws. Power is also supplied to a 120 voltstep down control transformer 62. Closing of a normally open startswitch 63 energizes a control relay 64 which functions to close motorcontrol contacts 64a for one of the motors 44 and also closes a holdingcircuit 64b, around the switch 63. A contact 640 is also closed tofurnish power to a small fan 65 to cool this power supply. To stop themotor controlled by relay 64, a normally closed stop switch 67 isopened. The other motor 44 is adapted to be started by closing of anormally open start switch 68 which energizes a relay 69 whereby toclose the relay contacts 69a for such other motor and also to close aholding circuit 69b around the switch 68. To stop this motor a normallyclosed stop switch 70 is opened. Respective rheostats 71 are provided tocontrol the speed of the motors 44. When the platform 10 is in zeroposition, that is straight on with the path of traverse movement, anormally open limit switch 72 is closed and a corresponding identifyinglamp in a battery of lamps 73 is illuminated. Closing of the switch 72provides a current path enabling a normally open push button switch 74to be closed whereby to energize a relay 75 and through relay contacts75a and 75b energizing relays 77 and 78 whereby to close contacts 77aand 78a for selector switches 79 for selectively controlling thesolenoids for the forward clutch 50 or the reverse clutch 51 as well asthe brake clutch v 55. At the same time, contacts 75c and 75d closebypass circuits around the rheostats 71 so that the motors 44 canoperate at top speed. Further, energizing of relays 77 and 78 effectsrelease of the motor brake 45.

When the platform 10 is in the rear landing and takeoff position,swiveling to one side or the other maybe effected by operating eitherselected one of the selector switches 79, respective limit switches 80controlling respective ones of the lamps 73 to identify the degree ofswiveling movement from the zero or straight-in-line position.

Should the degree of swiveling movement exceed desirable outside limits,such as 30, then an override limit switch 81 or 82, as the case may be,will be opened and thereby shut off power to the motor 44 involved. Suchmotor may be restarted by reversing the associated selector switch 79and depressing start button 63 and normally open pushbutton 83, or startbutton 68 and pushbutton 84. Either pushbutton 83 or 84, that isinvolved, must then be held down and a normally open pushbutton 85 or 87depressed. This will clear the override. As soon as the proper positionreadout light 73 illuminates, switch 83 or 84 can be released, andnormally closed limit switches 81 and 82 will again be in control.

In either the reverse or foreward closing of the selector switch'79 ineach instance, a respective clutch solenoid 55 is energized to releasethe normally on" brake 54 of the screw 20 selected to be operated.

From the foregoing it will be apparent that all maneuvers of theplatform 10 are adapted to be readily effected from a suitable controlstation by the several pushbutton controls in the system described inconnection with FIG. 7.

For helicopter landing pad purposes, the platform 10 may be providedwith a suitable landing target marking 90. In addition, the platform maybe provided with suitable anchoring devices for tie-down chains orcables 92 connected to the aircraft and which may be of a typeautomatically releasable by the pilot for take-off.

There is thus provided a safe, efficient, simple method of handlingheavy objects which must be transported along path between spacedpositions and which may necessarily be oriented angularly relative tothe path on approach to or departure from at least one of the positions,and comprising driving a swivel platform in a conveyor system along thepath to and between the positions, and at said one position swiveling orturning the platform to accommodate the angular orienation of theobject. This method is especially suited for handling aircraft of thegeneral vertical take-off and landing type-such as helicopters, and moreparticularly on shipboard, where the platform provides a snare pad.

Although various minor modifications might be suggested by those versedin the art, it should be understood that we wish to embody within thescope of the patent warranted hereon all such embodiments as reasonablyand properly come within the scope of our contribution to the art.

We claim as our invention:

1. A conveyor system for handling a heavy object which must betransported along a path between spaced positions and which maynecessarily be oriented angularly relative to said path on approach toor departure from at least one of said positions, comprising:

a platform on which the object is supported bodily for transportationalong said path;

a pair of spaced parallel tracks along said path between said positionsunder said platform;

a respective member to run along each of said tracks;

means for selectively driving said members along the respective tracks;

means swivelly connecting one of said members to the underside of saidplatform;

guide track means carried by the underside of said platform operativelyaligned with said swivelly connecting means and extending transverselyrelative to said pair of tracks; and

a runner block running along said track means and swivelly connected tothe other of said members;

whereby the platform can be moved along said parallel tracks byoperating the driving means for both of said members in unison, and theplatform can be swivelly moved by selectively operating the drivingmeans for either of said members, the platform swiveling about saidswivelly connecting means and said runner riding along said track meansto compensate for changes in angularity of the track means relative tothe tracks during the swivelling movements of the platform.

2. A conveyor system according to claim 1, including stabilizing trackmeans carried by the platform, additional members running along saidtracks, runner blocks running in said stabilizing track means, andswivel connections between said runner blocks and said additionalmembers.

3. A conveyor system according to claim 1, having a pair of theadditional members spaced from said respective members along saidtracks, and said stabilizing track means extending angulalry relative tothe direction of the guide track means.

4. A conveyor assembly according to claim 2, wherein said stabilizingtrack means comprise generally V-shaped inverted channel-shaped runnerbar assemblies in allochiral relative relationship at each side of saidguide track means and with each leg of each of the assembliesaccommodating a separate one of the runner blocks swivelly connected tosaid additional membets.

5. A conveyor system according to claim 1, wherein said driving meanscomprise respective rotary screws and means mounting the screws alongsaid tracks, said respective members having follower means engaging thescrews for actuation of the respective members by rotation of thescrews, means for driving the screws respectively in either oppositerotary direction, and means for selectively controlling said drivingmeans.

6. A conveyor system according to claim 5, wherein said means fordriving the screws comprise reversible motors, and brake means forholding either respective screw non-rotatively when its motor isnon-operating.

7. A conveyor system according to claim 6, wherein said controllingmeans comprise an electrical circuit for controlling the degree ofswivelling motion of said platform through control of operation of saidmotors and brake means.

8. A conveyor system according to claim 1, including hinged sideextensions on said platform projecting substantially laterally beyondthe respective opposite sides of the platform and hingedly swingableinto clearance relation over the sides of the platform from an extendedposition wherein the lateral dimensions of the platform aresubstantially increased.

9. A conveyor system according to claim 1, wherein said platformcomprises a landing pad including a rug ged frame and a deck structureon said frame, the landing pad being especially adapted for handlingaircraft of the vertical take-off and landing type and including meansfor anchoring the aircraft to the platform for transportation on theplatform between said positions.

10. A conveyor system according to claim 9, including a landing targetindicia on the upper surface of said platform to facilitate landing ofan aircraft accurately for support upon the platform.

11. In combination with a conveyor system according to claim 1, a flightdeck having one of said spaced positons in a landing area on said flightdeck, an aircraft hanger spaced from said one position and covering theother of said positions with an opening facing toward said one position,said platform comprising a vertical take-off and landing aircraftlanding pad having means for anchoring an aircraft thereon in supportedrelation on said platform, and said driving means operating to effecttransportation of the platform and an aircraft carried thereon to andbetween the interior of the hanger and said one position on the flightdeck.

12. A conveyor system according to claim 1, wherein said platformcomprises a rugged frame including longitudinal and transverse framebars, said track means comprising bar structure secured to thetransverse frame bars, and a deck structure carried on top of the framebars.

13. A conveyor system according to claim 1, wherein said tracks compriselongitudinally extending upwardly opening channels having longitudinallyextending vertical side walls, track bars extending longitudinally onsaid walls within said channels above the bottom of the channels, saidmembers having wheels thereon engaging upper and lower track surfaces ofsaid track bars.

14. A conveyor system according to claim 13, wherein said track means onthe platform comprise a downwardly opening elongated channel having sidewalls, longitudinally extending track bars on said track means channelside walls, and said runner block having rollers engaging said trackmeans channel track bars.

15. A method of handling a heavy object which must be transported alonga path between spaced positions and which article may necessarily beoriented angularly relative to said path on approach to or departurefrom at least one of said positions, comprising:

placing said object on a platform which is operatively coupled with apair of transporting long span screws extending along a pair of spacedparallel tracks extending along said path; operating said screws inunison to effect traverse of the platform along said path and therebytransportation of the article along said path; and

relatively operating said screws to effect swivelling movement of theplatform;

16. A method according to claim 15, including signalling the degrees ofswivelling movement of the platform relative to said path.

17. A method according to claim 15, wherein said object is an aircraftand said platform comprises a landing pad, said spaced positionscomprising a hanger and a landing and take-off area respectively, andincluding supporting the aircraft on the platform, connecting theaircraft releasably to the platform, and transporting the aircraft onsaid platform between said hanger and said area by operating said screwsin unison to effect transporting of the platform.

18. A method according to claim 15, wherein said platform comprises anaircraft landing pad and said object comprises an aircraft, includingsupporting said aircraft on said platform, and securing said aircraft tothe platform for transportation on the platform.

1. A conveyor system for handling a heavy object which must betransported along a path between spaced positions and which maynecessarily be oriented angularly relative to said path on approach toor departure from at least one of said positions, comprising: a platformon which the object is supported bodily for transportation along saidpath; a pair of spaced parallel tracks along said path between saidpositions under said platform; a respective member to run along each ofsaid tracks; means for selectively driving said members along therespective tracks; means swivelly connecting one of said members to theunderside of said platform; guide track means carried by the undersideof said platform operatively aligned with said swivelly connecting meansand extending transversely relative to said pair of tracks; and a runnerblock running along said track means and swivelly connected to the otherof said members; whereby the platform can be moved along said paralleltracks by operating the driving means for both of said members inunison, and the platform can be swivelly moved by selectively operatingthe driving means for either of said members, the platform swivelingabout said swivelly connecting means and said runner riding along saidtrack means to compensate for changes in angularity of the track meansrelative to the tracks during the swivelling movements of the platform.2. A conveyor system according to claim 1, including stabilizing trackmeans carried by the platform, additional members running along saidtracks, runner blocks running in said stabilizing track means, andswivel connections between said runner blocks and said additionalmembers.
 3. A conveyor system according to claim 2, having a pair of theadditional members spaced from said respective members along saidtracks, and said stabilizing track means extending angularly relative tothe direction of the guide track means.
 4. A conveyor assembly accordingto claim 2, wherein said stabilizing track means comprise generallyV-shaped inverted channel-shaped runner bar assemblies in allochiralrelative relationship at each side of said guide track means and witheach leg of each of the assemblies accommodating a separate one of therunner blocks swivelly connected to said additional members.
 5. Aconveyor system according to claim 1, wherein said driving meanscomprise respective rotary screws and means mounting the screws alongsaid tracks, said respective members hAving follower means engaging thescrews for actuation of the respective members by rotation of thescrews, means for driving the screws respectively in either oppositerotary direction, and means for selectively controlling said drivingmeans.
 6. A conveyor system according to claim 5, wherein said means fordriving the screws comprise reversible motors, and brake means forholding either respective screw non-rotatively when its motor isnon-operating.
 7. A conveyor system according to claim 6, wherein saidcontrolling means comprise an electrical circuit for controlling thedegree of swivelling motion of said platform through control ofoperation of said motors and brake means.
 8. A conveyor system accordingto claim 1, including hinged side extensions on said platform projectingsubstantially laterally beyond the respective opposite sides of theplatform and hingedly swingable into clearance relation over the sidesof the platform from an extended position wherein the lateral dimensionsof the platform are substantially increased.
 9. A conveyor systemaccording to claim 1, wherein said platform comprises a landing padincluding a rugged frame and a deck structure on said frame, the landingpad being especially adapted for handling aircraft of the verticaltake-off and landing type and including means for anchoring the aircraftto the platform for transportation on the platform between saidpositions.
 10. A conveyor system according to claim 9, including alanding target indicia on the upper surface of said platform tofacilitate landing of an aircraft accurately for support upon theplatform.
 11. In combination with a conveyor system according to claim1, a flight deck having one of said spaced positions in a landing areaon said flight deck, an aircraft hanger spaced from said one positionand covering the other of said positions with an opening facing towardsaid one position, said platform comprising a vertical take-off andlanding aircraft landing pad having means for anchoring an aircraftthereon in supported relation on said platform, and said driving meansoperating to effect transportation of the platform and an aircraftcarried thereon to and between the interior of the hanger and said oneposition on the flight deck.
 12. A conveyor system according to claim 1,wherein said platform comprises a rugged frame including longitudinaland transverse frame bars, said track means comprising bar structuresecured to the transverse frame bars, and a deck structure carried ontop of the frame bars.
 13. A conveyor system according to claim 1,wherein said tracks comprise longitudinally extending upwardly openingchannels having longitudinally extending vertical side walls, track barsextending longitudinally on said walls within said channels above thebottom of the channels, said members having wheels thereon engagingupper and lower track surfaces of said track bars.
 14. A conveyor systemaccording to claim 13, wherein said track means on the platform comprisea downwardly opening elongated channel having side walls, longitudinallyextending track bars on said track means channel side walls, and saidrunner block having rollers engaging said track means channel trackbars.
 15. A method of handling a heavy object which must be transportedalong a path between spaced positions and which article may necessarilybe oriented angularly relative to said path on approach to or departurefrom at least one of said positions, comprising: placing said object ona platform which is operatively coupled with a pair of transporting longspan screws extending along a pair of spaced parallel tracks extendingalong said path; operating said screws in unison to effect traverse ofthe platform along said path and thereby transportation of the articlealong said path; and relatively operating said screws to effectswivelling movement of the platform;
 16. A method according to claim 15,including signalling the degrees of swivelling movement of the platfOrmrelative to said path.
 17. A method according to claim 15, wherein saidobject is an aircraft and said platform comprises a landing pad, saidspaced positions comprising a hanger and a landing and take-off arearespectively, and including supporting the aircraft on the platform,connecting the aircraft releasably to the platform, and transporting theaircraft on said platform between said hanger and said area by operatingsaid screws in unison to effect transporting of the platform.
 18. Amethod according to claim 15, wherein said platform comprises anaircraft landing pad and said object comprises an aircraft, includingsupporting said aircraft on said platform, and securing said aircraft tothe platform for transportation on the platform.